APOPHIS

FROM WIKIPEDIA AT: http://en.wikipedia.org/wiki/Aten_asteroids

The Aten asteroids are a group of near-Earth asteroids (NEO's), named after the first of the group to be discovered (2062 Aten, discovered January 7, 1976, by Eleanor F. Helin). They are defined by having semi-major axes of less than one astronomical unit (the distance from the Earth to the Sun). Note that, because asteroids' orbits can be highly eccentric, an Aten orbit need not be entirely contained within Earth's orbit; in fact, nearly all known Aten asteroids have their aphelion greater than one AU.

Asteroids that have their aphelion entirely within the Earth's orbit are known as Apohele asteroids, or alternatively as Inner Earth Objects (IEOs) or Atira asteroids. Apoheles are traditionally treated as a subclass of Atens,[1] but sometimes are separated.[2] As of June 2010, there are only ten known Apoheles, and 568 more known Aten asteroids.[2] The smallest aphelion is that of 2008 EB26), at 0.804 AU. The shortest semi-major axis for any known Aten asteroid is that of another Apohele, 2007 EA32), at 0.550 AU.

The Aten asteroid with the smallest known perihelion is also the one with the highest known eccentricity: (137924) 2000 BD19 has an orbit with an eccentricity of 0.895, which takes it from a perihelion of 0.092 AU, well within Mercury's orbit, to an aphelion of 1.661 AU.

For a brief time near the end of 2004, the asteroid 99942 Apophis (then known only by its provisional designation 2004 MN4) appeared to pose a threat of causing an Earth impact event in 2029, but earlier observations were found that eliminated that possibility, although a very small possibility remains for 2036 depending upon what happens to Aten's orbit after the 2029 encounter.

SEE THE NASA ARTICLE BELOW THIS ONE.

See Also

References

  1. ^ "List Of Aten Minor Planets". Minor Planet Center. 2010-02-12. http://www.cfa.harvard.edu/iau/lists/Atensq.html. Retrieved 2010-06-05.

  2. ^ a b "NEO Discovery Statistics". Minor Planet Center. 2010-06-02. http://neo.jpl.nasa.gov/stats/. Retrieved 2010-06-05.

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See also: List of minor planets, Meanings of minor planet names, Pronunciation of asteroid names, and Solar System

ARTICLE BELOW IS ALSO FROM WIKIPEDIA:

99942 Apophis (pronounced /əˈpɒfɪs/, previously known by its provisional designation 2004 MN4) is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a small probability (up to 2.7%) that it would strike the Earth in 2029. Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a precise region in space no more than about 600 meters across[6], that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis will pass through the keyhole was determined to be very small. Apophis broke the record for the highest level on the Torino Scale, being, for only a short time, a level 4, before it was lowered.[7] Its diameter is approximately 270 meters (885 ft).[2]

Keyhole

Additional observations of the trajectory of Apophis revealed the keyhole will probably be missed. On August 5, 2006, Apophis was lowered to a Level 0 on the Torino Scale. As of October 7, 2009, the impact probability for April 13, 2036, is calculated as 1 in 250,000.[8] An additional impact date in 2068 was also identified; the impact probability for that encounter is calculated as 3 in a million.[3][8]

Space probe

Many scientists agree that Apophis warrants closer scrutiny. To that end, in February 2008 the Planetary Society awarded $50,000 in prize money to companies and students who submitted designs for space probes that would put a tracking device on or near the asteroid.[9] Several other groups have studied or plan to study missions to Apophis.

Basic data

Based upon the observed brightness, Apophis' length was estimated at 450 metres (1,480 ft); a more refined estimate based on spectroscopic observations at NASA's Infrared Telescope Facility in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is 350 metres (1,150 ft).

In October 2005 it was predicted that the asteroid will pass just below the altitude of geosynchronous satellites, which are at 35,786 kilometres (22,236 mi). Such a close approach by an asteroid of this size is expected to occur only every 1,300 years or so. Apophis’ brightness will peak at magnitude 3.3, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter will be ~2 arcseconds, so that it will be barely resolved by telescopes not equipped with adaptive optics.

Naming

When first discovered, the object received the provisional designation 2004 MN4 (sometimes written 2004 MN4), and news and scientific articles about it referred to it by that name. When its orbit was sufficiently well calculated, it received the permanent number 99942 (on June 24, 2005). Receiving a permanent number made it eligible for naming, and it received the name "Apophis" on July 19, 2005. Apophis is the Greek name of the Ancient Egyptian enemy of Ra: Apep, the Uncreator, a serpent that dwells in the eternal darkness of the Duat (earth's middle) and tries to swallow Ra during His nightly passage. Apep is held at bay by Set, the Ancient Egyptian god of Chaos.

Although the Greek name for the Egyptian god may be appropriate, Tholen and Tucker — two of the co-discoverers of the asteroid — are reportedly fans of the TV series Stargate SG-1. One of the show's persistent villains is an alien also named for the Egyptian god.[10]

Close approaches

After the Minor Planet Center confirmed the June discovery of Apophis, an April 13, 2029 close approach was flagged by NASA's automatic Sentry system and NEODyS, a similar automatic program run by the University of Pisa and the University of Valladolid. On that date, it will become as bright as magnitude 3.3 (visible to the naked eye from rural as well as darker suburban areas, visible with binoculars from most locations[11]). This close approach will be visible from Europe, Africa, and western Asia. As a result of its close passage, it will move from the Aten to the Apollo class.

After Sentry and NEODyS announced the possible impact, additional observations decreased the uncertainty in Apophis' trajectory. As they did, the probability of an impact event temporarily climbed, peaking at 2.7% (1 in 37). Combined with its size, this caused Apophis to be assessed at level 4 on the Torino Scale and 1.10 on the Palermo scale, scales scientists use to represent the danger of an asteroid hitting Earth. These are the highest values for which any object has been rated on either scale.

On Friday, April 13, 2029, Apophis will pass Earth within the orbits of geosynchronous communication satellites.[12] It will return for another close Earth approach in 2036.

Precovery observations from March 15, 2004, were identified on December 27, and an improved orbit was computed.[13] Radar astrometry further refined the orbit. The 2029 pass will actually be much closer than the first predictions, but the uncertainty is such that an impact is ruled out. Similarly, the pass on April 13, 2036 carries little risk of an impact.

2013 refinement

The close approach in 2029 will substantially alter the object's orbit, making predictions uncertain without more data. "If we get radar ranging in 2013 [the next good opportunity], we should be able to predict the location of 2004 MN4 out to at least 2070." said Jon Giorgini of JPL.[14] Apophis will pass within 0.09666 AU (14.4 million km,8.9 million mi.) of the Earth in 2013 allowing astronomers to refine the trajectory for future close passes.[15][16]

In July 2005, former Apollo astronaut Rusty Schweickart, as chairman of the B612 Foundation, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance with Earth, which would increase the probability of future impacts. Schweickart asked for an investigation of the necessity of placing a transponder on the asteroid for more accurate tracking of how its orbit is affected by the Yarkovsky effect.[17]

History of impact estimates

Close approach of Apophis on April 13, 2029

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The white bar indicates uncertainty in the range of positions

99942 Apophis

Illustration of a common trend where progressively reduced uncertainty regions result in an asteroid impact probability increasing followed by a sharp decrease.

    • The original NASA report on December 23, 2004, mentioned impact chances of "around 1 in 300" in 2029, which was widely reported in the media.[7] The actual NASA estimates at the time were 1 in 233; they resulted in the Torino scale rating of 2, the first time any asteroid had received a rating above 1.

    • Later that day, based on a total of 64 observations, the estimates were changed to 1 in 62 (1.6%), resulting in an update to the initial report and an upgrade to a Torino scale rating of 4.

    • On December 25, 2004, the chances were first reported as 1 in 42 (2.4%) and later that day (based on 101 observations) as 1 in 45 (2.2%). At the same time, the asteroid's estimated diameter was lowered from 440 m to 390 m and its mass from 1.2×1011 kg to 8.3×1010 kg.

    • On December 26, 2004 (based on a total of 169 observations), the impact probability was still estimated as 1 in 45 (2.2%), the estimates for diameter and mass were lowered to 380 m and 7.5×1010 kg, respectively.

    • On December 27, 2004 (based on a total of 176 observations), the impact probability was raised to 1 in 37 (2.7%); diameter was increased to 390 m, and mass to 7.9×1010 kg.

    • On December 27, 2004, in the afternoon, a precovery increased the span of observations to 287 days and allowed more accurate calculations to re-rate the asteroid's 2029 approach as level zero on the Torino scale (no threat). The cumulative impact probability was estimated to be around 0.004%, a lower risk than asteroid 2004 VD17, which once again became the greatest risk object. A 2053 approach to Earth still poses a minor risk of impact, and Apophis was still rated at level one on the Torino scale for this orbit, and thus remains that way.

    • On December 28, 2004 at 12:23 GMT and (based on a total of 139 observations), produced a value of one on the Torino scale for 2044-04-13.29 and 2053-04-13.51.

    • By 01:10 GMT on December 29, 2004 the only pass rated 1 on the Torino scale was for 2053-04-13.51 based on 139 observations spanning 287.71 days (2004-Mar-15.1104 to 2004-Dec-27.8243). (As of 2010, the 2053 is now a 2056-04-13 risk of 1 in 10 million.)[3]

    • By 19:18 GMT on December 29, 2004 this was still the case based upon 147 observations spanning 288.92 days (2004-Mar-15.1104 to 2004-Dec-29.02821), though the close encounters have changed and been reduced to 4 in total.

    • By 13:46 GMT on December 30, 2004 no passes were rated above 0, based upon 157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). The most dangerous pass was rated at 1 in 7,143,000.

    • By 22:34 GMT on December 30, 2004, 157 observations spanning 289.33 days (2004-Mar-15.1104 to 2004-Dec-29.44434). One pass at 1 (Torino scale) 3 other passes.

    • By 03:57 GMT on January 2, 2005, 182 observations spanning 290.97 days (2004-Mar-15.1104 to 2004-Dec-31.07992) One pass at 1 (Torino scale) 19 other passes.

    • By 14:49 GMT on January 3, 2005, observations spanning 292.72 days (2004-Mar-15.1104 to 2005-Jan-01.82787) One pass at 1 (Torino scale) 15 other passes.

    • Extremely precise radar observations at Arecibo Observatory on January 27, 28, and 30 refine the orbit further and show that the April, 2029 close approach will occur at only 5.6 Earth radii, approximately one-half the distance previously estimated.

    • A radar observation on August 7, 2005, refines the orbit further and eliminates the possibility of an impact in 2035. Only the pass in 2036 remains at Torino Scale 1.

    • A new radar observation at Arecibo Observatory on May 6, 2006, slightly lowered the Palermo scale rating, but the pass in 2036 remained at Torino Scale 1 despite the impact probability dropping by a factor of four.[18]

    • Additional observations through 2006 resulted in Apophis being lowered to Torino Scale 0 on August 6, 2006. Around this time, the impact probability was lowered to 1 in 45,000.

    • As of October 7, 2009, refinements to the precovery images of Apophis by the University of Hawaii's Institute for Astronomy, the 90-inch Bok Telescope, and the Arecibo Observatory have generated a refined path that reduces the odds of a April 13, 2036 impact to about 1 in 250,000.[3][8]

Possible impact effects

NASA initially estimated the energy that Apophis would have released if it struck Earth as the equivalent of 1480 megatons of TNT. A later, more refined NASA estimate was 880 megatons, then revised to 510 megatons.[3] The impacts which created the Barringer Crater or the Tunguska event are estimated to be in the 3–10 megaton range[19] The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons. In comparison, the Chicxulub impact, believed by many to be a significant factor in the extinction of the dinosaurs, has been estimated to have released about as much energy as 100,000,000 megatons.

Path of risk where 99942 Apophis may impact Earth in 2036.

The exact effects of any impact would vary based on the asteroid's composition, and the location and angle of impact. Any impact would be extremely detrimental to an area of thousands of square kilometres, but would be unlikely to have long-lasting global effects, such as the initiation of an impact winter[citation needed].

The B612 Foundation made estimates of Apophis' path if a 2036 Earth impact were to occur as part of an effort to develop viable deflection strategies.[20] The result is a narrow corridor a few miles wide, called the "path of risk", extending across southern Russia, across the north Pacific (relatively close to the coastlines of California and Mexico), then right between Nicaragua and Costa Rica, crossing northern Colombia and Venezuela, ending in the Atlantic, just before reaching Africa.[21][22] Using the computer simulation tool NEOSim, it was estimated that the hypothetical impact of Apophis in countries such as Colombia and Venezuela, which are in the path of risk, could have more than 10 million casualties.[23] An impact several thousand miles off the West Coast of the US would produce a devastating tsunami.[24]

Potential space missions

Planetary Society competition

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In 2008, The Planetary Society, a California-based space advocacy group, organized a $50,000 competition to design an unmanned space probe that would 'shadow' Apophis for almost a year, taking measurements that would "determine whether it will impact Earth, thus helping governments decide whether to mount a deflection mission to alter its orbit." The society received 37 entries from 20 countries on 6 continents.

The commercial competition was won by a design called 'Foresight' created by SpaceWorks Engineering.[9] SpaceWorks proposes a simple orbiter with only two instruments and a radio beacon at a cost of ~140 million USD, launched aboard a Minotaur IV between 2012 and 2014, to arrive at Apophis five to ten months later. It would then rendezvous with, observe, and track the asteroid.

Foresight would orbit the asteroid to gather data with a multi-spectral imager for one month. It would then leave orbit and fly in formation with Apophis around the Sun at a range of two kilometers (1.2 miles). The spacecraft would use laser ranging to the asteroid and radio tracking from Earth for ten months to accurately determine the asteroid's orbit and how it might change.

Pharos, the winning student entry, would be an orbiter with four science instruments (a multi-spectral imager, near-infrared spectrometer, laser rangefinder, and magnetometer) that would rendezvous with and track Apophis. Earth-based tracking of the spacecraft would then allow precise tracking of the asteroid. The Pharos spacecraft would also carry four instrumented probes that it would launch individually over the course of two weeks. Accelerometers and temperature sensors on the probes would measure the seismic effects of successive probe impacts, a creative way to explore the interior structure and dynamics of the asteroid.

Second place, for $10,000, went to a European team led by Deimos Space S.L. of Madrid, Spain, in cooperation with EADS Astrium, Friedrichshafen, Germany; University of Stuttgart, Germany; and Università di Pisa, Italy. Juan L. Cano was Principal Investigator.

Another European team took home $5,000 for third place. Their team lead was EADS Astrium Ltd, United Kingdom, in conjunction with EADS Astrium SAS, France; IASF-Roma, INAF, Rome, Italy; Open University, UK; Rheinisches Institut für Umweltforschung, Germany; Royal Observatory of Belgium; and Telespazio, Italy. The Principal Investigator was Paolo D'Arrigo.

Two teams tied for second place in the Student Category: Monash University, Clayton Campus, Australia, with Dilani Kahawala as Principal Investigator; and University of Michigan, with Jeremy Hollander as Principal Investigator. Each second place team won $2,000. A team from Hong Kong Polytechnic University and Hong Kong University of Science and Technology, under the leadership of Peter Weiss, received an honorable mention and $1,000 for the most innovative student proposal.

[edit] Proposed deflection strategies

Studies by NASA, ESA,[25] and various research groups in addition to the Planetary Society contest teams,[26] have described a number of proposals for deflecting Apophis or similar objects, including gravitational tractor, kinetic impact, and nuclear bomb methods.

On December 30, 2009, Anatoly Perminov, the director of the Russian Federal Space Agency, said in an interview that Roscosmos will also study designs for a possible deflection mission to Apophis.[27]

[edit] Don Quijote mission

Apophis is one of two asteroids under consideration by the European Space Agency as the target of its Don Quijote mission to study the effects of impacting an asteroid.[28]

References

External links

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Categories: Aten asteroids | Near-Earth asteroids | Asteroids named from Egyptian mythology | Potential impact events caused by Near-Earth objects | Discoveries by Roy A. Tucker | Astronomical objects discovered in 2004

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DATA AND ARTICLE BELOW ARE FROM NASA

Predicting Apophis' Earth Encounters in 2029 and 2036

SUMMARY

Researchers at NASA/JPL, Caltech, and Arecibo Observatory have released the results of radar observations of the potentially hazardous asteroid 99942 Apophis, along with an in-depth analysis of its motion. The research will affect how and when scientists measure, predict, or consider modifying the asteroid's motion. The paper has been accepted for publication in the science journal "Icarus" and was presented at the AAS/DPS conference in Orlando, Florida in October of 2007. The Apophis study was led by Jon Giorgini, a senior analyst in JPL's Solar System Dynamics group and member of the radar team that observed Apophis.

The analysis of Apophis previews situations likely to be encountered with NEAs yet to be discovered: a close approach that is not dangerous (like Apophis in 2029) nonetheless close enough to obscure the proximity and the danger of a later approach (like Apophis in 2036) by amplifying trajectory prediction uncertainties caused by difficult-to-observe physical characteristics interacting with solar radiation as well as other factors.

BACKGROUND

Upon its discovery in 2004, Apophis was briefly estimated to have a 2.7% chance of impacting the Earth in 2029. Additional measurements later showed there was no impact risk at that time from the 210-330 meter (690-1080 foot) diameter object, identified spectroscopically as an Sq type similar to LL chondritic meteorites. However, there will be a historically close approach to the Earth, estimated to be a 1 in 800 year event (on average, for an object of that size).

The Arecibo planetary radar telescope subsequently detected the asteroid at distances of 27-40 million km (17-25 million miles; 0.192-0.268 AU) in 2005 and 2006. Polarization ratios indicate Apophis appears to be smoother than most NEAs at 13-cm scales. Including the high precision radar measurements in a new orbit solution reduced the uncertainty in Apophis' predicted location in 2029 by 98%.

While trajectory knowledge was substantially corrected by the Arecibo data, a small estimated chance of impact (less than 1 in 45,000 using standard dynamical models) remained for April 13, 2036. With Apophis probably too close to the Sun to be measured by optical telescopes until 2011, and too distant for useful radar measurement until 2013, the underlying physics of Apophis' motion were considered to better understand the hazard.

Arecibo Radar Image of Apophis

Apophis Position Uncertainty

RESULTS OF THE STUDY(1) Extending the "Standard Dynamical Model"

Trajectory predictions for asteroids are normally based on a standard model of the solar system that includes the gravity of the Sun, Moon, other planets, and the three largest asteroids.

However, additional factors can influence the predicted motion in ways that depend on rarely known details, such as the spin of the asteroid, its mass, the way it reflects and absorbs sun-light, radiates heat, and the gravitational pull of other asteroids passing nearby. These were examined, along with the effect of Earth's non-uniform gravity field during encounters, and limitations of the computer hardware performing the calculations.

One would normally look for the influence of such factors as they gradually alter the trajectory over years. But, for Apophis, the changes remain small until amplified by passage through Earth's gravity field during the historically close approach in 2029.

For example, the team found solar energy can cause between 20 and 740 km (12 and 460 miles) of position change over the next 22 years leading into the 2029 Earth encounter. But, only 7 years later, the effect on Apophis' predicted position can grow to between 520,000 and 30 million km (323,000 and 18.6 million miles; 0.0035-0.2 AU). This range makes it difficult to predict if Apophis will even have a close encounter with Earth in 2036 when the orbital paths intersect.

It was found that small uncertainties in the masses and positions of the planets and Sun can cause up to 23 Earth radii of prediction error for Apophis by 2036.

The standard model of the Earth as a point mass can introduce up to 2.9 Earth radii of prediction error by 2036; at least the Earth's oblateness must be considered to predict an impact.

The gravity of other asteroids can cause up to 2.3 Earth radii of prediction uncertainty for Apophis.

By considering the range of Apophis' physical characteristics and these error sources, it was determined what observations prior to 2029 will most effectively reduce prediction uncertainties. Observing criteria were developed that, if satisfied, could permit eliminating the 2036 impact possibility without further physical characterization of Apophis.

Such observations could reduce the need for a visit by an expensive spacecraft and reduce the risk of Apophis being prematurely eliminated as a hazard under the standard model, only to drift back into the hazard classification system years later as the smaller, unmodeled forces act upon it.

(2) Mitigation

Mitigation was not specifically studied, but the team found small variations in the energy absorption and reflection properties of Apophis' surface are sufficient to cause enough trajectory change to obscure the difference between an impact and a miss in 2036. Changing the amount of energy Apophis absorbs by half a percent as late as 2018 - for example by covering a 40 x 40 meter (130 x 130 foot) patch with lightweight reflective materials (an 8 kg payload) - can change its position in 2036 by a minimum of one Earth radius.

A change somewhat greater than this minimum would be required to allow for prediction uncertainties. For Apophis, scaling up to distribute 250 kg (550 pounds) of a reflective or absorptive material (similar to the carbon fiber mesh being considered for solar sails) across the surface could use the existing radiation forces to produce a 6-sigma trajectory change, moving at least "99.9999998" percent of the statistically possible trajectories away from the Earth in just 18 years.

While no deflection is expected to be necessary, the team's research demonstrates that any deflection method must produce a change known in advance to be greater than all the error sources in the prediction, including some greater than those considered with the standard model.

(3) Impact probability

The study did NOT compute new impact probabilities. This is because important physical parameters (such as mass and spin pole) that affect its trajectory have not yet been measured and hence there are no associated probability distributions. The study characterizes how the Standard Dynamical Model can over or under-estimate impact probability for those objects having close planetary encounters prior to the potential impact.

The situation is similar to having 6 apples (the measured Apophis parameters) and 6 boxes whose contents are unknown (the unmeasured Apophis parameters), then trying to compute the probability one has a total of 12 apples (impact probability). The result reflects back what is assumed about the unknown contents of the boxes, but doesn't reveal new information. The contents of the boxes must be observed (measured) to learn something new.

For similar reasons, the Apophis study instead uses the minimum and maximum range-of-effect in place of computing impact probabilities to provide reasonable criteria for excluding impact in the absence of detailed physical knowledge, once new position measurements are obtained at six key times.

(4) Non-Apophis Conclusions

Aspects of the study relevant to asteroids other than Apophis:

    • The Standard Dynamical Model can misestimate impact risk for the more numerous sub-km objects preceded by close planetary encounter(s). This problem might be addressed by reassessing impact potential after planetary encounters, given new measurements.

    • The minimum-maximum effect of unmeasured parameters can provide enough information to exclude threats in certain cases, even if a realistic impact probability cannot be computed.

    • Amplification of small trajectory offsets makes valid prediction across a close-encounter difficult without physical knowledge, but offers the potential to redirect the entire uncertainty region and has significant implications for costly spacecraft missions.

    • A deflection effort must be known in advance to produce change greater than predicted uncertainties due to ALL parameters, not only the Standard Dynamical Model. For example, if a method produces 10 Earth-radii of change, but prediction uncertainties from all sources are 20 Earth-radii, the deflection would move the asteroid around within the noise, producing an unpredicted result or even a new hazard.

The Apophis situation has predictability problems essentially the same as previously described in "Science" for 29075 (1950 DA), but occurring more severely: in as little as 2-3 decades, rather than the 880 year prediction of that case.

FUTURE

The future for Apophis on Friday, April 13 of 2029 includes an approach to Earth no closer than 29,470 km (18,300 miles, or 5.6 Earth radii from the center, or 4.6 Earth-radii from the surface) over the mid-Atlantic, appearing to the naked eye as a moderately bright point of light moving rapidly across the sky. Depending on its mechanical nature, it could experience shape or spin-state alteration due to tidal forces caused by Earth's gravity field.

This is within the distance of Earth's geosynchronous satellites. However, because Apophis will pass interior to the positions of these satellites at closest approach, in a plane inclined at 40 degrees to the Earth's equator and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it does not threaten the satellites in that heavily populated region.

Using criteria developed in this research, new measurements possible in 2013 (if not 2011) will likely confirm that in 2036 Apophis will quietly pass more than 49 million km (30.5 million miles; 0.32 AU) from Earth on Easter Sunday of that year (April 13).

CREDITS

In addition to Giorgini, co-authors of the report include Dr. Lance A. M. Benner and Dr. Steven J. Ostro of JPL; Dr. Michael C. Nolan, Arecibo Observatory, Puerto Rico, and Michael W. Busch of the California Institute of Technology.

Arecibo Observatory is operated by Cornell University under a cooperative agreement with the National Science Foundation. JPL is managed for NASA by the California Institute of Technology in Pasadena.

UPDATE NOTES

Asteroid Apophis in the News Again

by Nancy Atkinson on January 27, 2011

From UNIVERSETODAY.COM

Apophis Trajectory Change

Present era through 2029

Small factors 2029-2036

Animation of Apophis. Image Credit: Observatorio Astronomico Sormano

It must have been a slow news day in Russia on 2011 Jan 26 (actually – and unfortunately — it wasn’t)… as headlines from one of Russia’s leading news agencies, Ria Novosti, proclaimed, “Russian Astronomers Predict Apophis-Earth Collision in 2036.” But reading the article a little further, the astronomer, Leonid Sokolov of St. Petersburg State University says the chance of a collision in 2036 is extremely slim, which is exactly what NASA’s Near-Earth Object Program has been saying for several years. So, just to be clear, there is no new information or changes in understanding Apophis’ orbit. Here are the facts:

Apophis is expected to make a record-setting — but harmless — close approach to Earth on Friday, April 13, 2029 when it comes no closer than 29,450 km from Earth (18,300 miles). Astronomers have ruled out any possibility of an impact in 2029.

That close pass could alter the asteroid’s orbit for future passes by Earth, but the exact course of the new orbit will depend on exactly how close Apophis comes to Earth in 2029.

That being said, with all the different orbital parameters taken in to account, the probability of Apophis impacting Earth on its following pass in 2036 is about 1 in 250,000, as of the estimates released in October of 2009.

This animation illustrates how the unmeasured physical parameters of Apophis bias the entire statistical uncertainty region. Credit: NASA/JPL

Another encounter by the asteroid with Earth in 2068 currently has a chance of impact at approximately 1 in 333,000.

Like all preliminary estimates, NASA says it is expected that the 2068 encounter will diminish in probability as more information about the 2029 pass by Apophis is acquired.

Initially, when first discovered in 2004, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029, but as scientists have made better and more detailed observations, they were able to recalculate the path of Apophis, determining that there was no chance it would hit Earth in 2029 and significantly downgrading the odds of it hitting Earth on future passes.

“The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared,” said Don Yeomans, manager of the NEO Program Office at JPL. “The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed.”

Apophis is approximately Its diameter is approximately 270 meters (885 ft), the size of two-and-a-half football fields.

See more information from NASA’s NEO office.

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2009-Apr-29:

This animation illustrates how the unmeasured physical parameters of Apophis bias the entire statistical uncertainty region. If Apophis is a RETROGRADE rotator on the small, less-massive end of what is possible, the measurement uncertainty region will get pushed back such that the center of the distribution encounters the Earth's orbit. This would result in an impact probability much higher than computed with the Standard Dynamical Model. Conversely, if Apophis is a small, less-massive PROGRADE rotator, the uncertainty region is advanced along the orbit. Only the remote tails of the probability distribution could encounter the Earth, producing a negligible impact probability. Although measurements in 2010-2011 may cut the size of the measurement uncertainty region greatly and result in an "all clear" using the Standard Dynamical Model, it may not be until Arecibo radar in 2013 provides a spin direction that Earth's passage through the probability distribution center can be ruled out.

2008-Jul-10:

An equivalent way of describing the problem of computing an impact probability for Apophis is that the true 2029 "keyhole" leading to a 2036 impact -- as compared to the theoretical keyhole derived from the Standard Dynamical Model -- is not known in the absence of knowledge of the complete dynamics. The problem is acute enough for Apophis that, IF impact hasn't been previously excluded, AND there hasn't been a through physical characterization, it can't be known for certain it will impact until during or after the 2029 encounter, even if a spacecraft is accompanying Apophis and providing position measurements good to 2 meters. That is, the keyhole could be determined only retrospectively, after passage through it.

2008-Apr-16:

In response to inquiries, accidental impact with an artifical satellite in 2029 is vanishingly unlikely. As mentioned above, (1) Apophis does not pass near the zones where most satellites are located and (2) man-made satellites and Apophis both have small cross-sectional areas. Even if a high-velocity impact occurred, at most a large satellite could change Apophis' position 7 years later (in 2036) by only 100's of km. This is less than 1/10th the size of the smaller issues considered in the study, very much in the noise of the calculations, and can have no meaningful effect on Earth impact probability estimation (which already incorporates more than 30 million km of uncertainty). At such a late date, impact with an artificial satellite would be like a bug on the windshield of Apophis. Deflection efforts are dependent on being early enough to leverage the dynamics of the 2029 encounter. Events during the encounter lack such leverage.

2008-Feb-22:

Paper received JPL's 2008 Edward Stone Award for Outstanding Research Publication.

2007-Dec-13:

The paper will be published in the January 2008 issue of Icarus. Reference: Giorgini JD, Benner LAM, Ostro SJ, Nolan MC, Busch MW, Predicting the Earth encounters of (99942) Apophis, Icarus 193 (2008), pp. 1-19.

Site Manager: Don Yeomans

Webmaster: Ron Baalke

Last Updated: 28 Dec 2009

Perturbations & Predicted Uncertainties for Apophis

The plot shows two things:

    • Predicted development of Apophis' position uncertainty over time (blue, red, black lines).

    • Optical measurements made in 2011 are expected to cut uncertainties in half. Optical and radar measurements in 2013 should reduce uncertainties below 50 km. If Arecibo is able to determine a shape and pole, uncertainties could be reduced 94% relative to optical data only.

  • Minimum/maximum effects of dynamics not considered in the Standard Dynamical Model (gold lines).

    • These dynamics could be visible in 2013, especially in Arecibo measurements, depending on their magnitude. Prior to then, the changes will be too small to be detected by even the best ground-based measurements.

Figure by J. Giorgini (JPL).

-----------------------------------------------------------------------------------------------------------------------------------

- Maximum prediction error by 2036 due to factors not considered in the Standard Dynamical Model (other than solar radiation). These smaller error sources remain less than 3 km by 2029, but are amplified to as much as 23 Earth-radii only 7 years later by Earth's gravity field during the close-approach. Figure by J. Giorgini (JPL).

-----------------------------------------------------------------------------------------------------------------------------------

NEA Orbital Elements

Switch to Near-Earth Comet (NEC) table.

NEAs (Near-Earth Asteroids) Amors Apollos Atens IEO (Interior Earth Object) PHAs (Potentially Hazardous Asteroids)

Sort by object number/name Sort by semi-major axis (a) Sort by eccentricity (e) Sort by inclination (i) Sort by argument of perihelion (w) Sort by long. of the ascending node Sort by mean anomaly (M) Sort by perihelion distance (q) Sort by aphelion distance (Q) Sort by orbital period (P) Sort by absolute magnitude (H) Sort by Earth MOID

10 rows per page max. 20 rows per page max. 50 rows per page max. 100 rows per page max. 200 rows per page max. 500 rows per page max. unlimited rows per page show full table

no H limit H <= 14 H <= 16 H <= 18 H <= 20 H <= 22 H <= 24 H <= 26

Ascending Sort Descending Sort

The table below provides J2000 heliocentric ecliptic orbital elements

for 20 of 6646 NEAs (Near-Earth Asteroids) sorted by object number/name.

First/Previous/Next/Last Page (rows 401 to 420 shown)

a

(AU)

1.87

1.46

0.73

1.65

0.92

2.60

2.64

2.27

1.78

1.62

2.03

1.13

2.13

1.84

0.91

1.42

2.44

2.15

1.60

1.24

e

0.507

0.276

0.595

0.645

0.191

0.699

0.626

0.554

0.408

0.611

0.393

0.204

0.466

0.581

0.817

0.189

0.759

0.615

0.271

0.361

i

(deg)

10.6

7.6

28.8

12.8

3.3

16.3

2.8

11.5

24.2

4.8

45.8

6.0

7.5

38.5

32.5

14.8

10.4

14.3

16.4

20.9

w

(deg)

61.2

249.7

2.8

322.8

126.4

12.1

38.2

311.6

138.7

268.6

295.2

66.2

220.3

103.9

281.5

115.8

40.9

11.6

343.7

343.9

Node

(deg)

284.4

122.5

225.6

16.5

204.4

77.3

308.5

176.9

221.2

111.1

128.9

2.1

72.7

116.8

237.5

123.8

164.1

163.5

267.3

172.1

M

(deg)

72.9

16.0

320.5

9.5

339.9

63.7

4.8

175.2

254.1

1.6

138.5

163.2

164.9

323.1

67.8

261.2

103.2

264.2

94.4

187.0

q

(AU)

0.919

1.059

0.295

0.587

0.746

0.782

0.987

1.012

1.056

0.632

1.231

0.897

1.140

0.772

0.167

1.152

0.587

0.828

1.169

0.790

Q

(AU)

2.81

1.86

1.16

2.72

1.10

4.41

4.29

3.52

2.51

2.62

2.83

1.36

3.13

2.92

1.66

1.69

4.29

3.47

2.04

1.68

P

(yr)

2.55

1.77

0.62

2.13

0.89

4.19

4.28

3.41

2.38

2.07

2.89

1.20

3.12

2.50

0.87

1.69

3.80

3.15

2.03

1.37

H

(mag)

16.07

18.10

17.80

15.87

19.70

16.34

17.62

16.10

16.49

19.27

16.27

20.81

17.47

16.54

15.54

18.73

16.06

15.95

17.87

17.67

MOID

(AU)

0.047171

0.121223

0.155561

0.167171

0.000032

0.173704

0.014505

0.097156

0.129953

0.001712

0.437748

0.002326

0.148508

0.043649

0.355708

0.214500

0.122877

0.134171

0.161721

0.192190

ref

38

40

50

152

144

42

78

39

31

51

43

63

57

42

117

35

52

36

137

50

class

APO*

AMO

ATE

APO

ATE*

APO

APO*

APO

AMO

APO*

AMO

APO*

AMO

APO*

ATE

AMO

APO

APO

AMO

APO

99248 (2001 KY66)

99799 (2002 LJ3)

99907 (1989 VA)

99935 (2002 AV4)

99942 Apophis

100004 (1983 VA)

100085 (1992 UY4)

100756 (1998 FM5)

100926 (1998 MQ)

101869 (1999 MM)

101873 (1999 NC5)

101955 (1999 RQ36)

102873 (1999 WK11)

103067 (1999 XA143)

105140 (2000 NL10)

105141 (2000 NF11)

106538 (2000 WK63)

106589 (2000 WN107)

108519 (2001 LF)

108906 (2001 PL9)

First/Previous/Next/Last Page (rows 401 to 420 shown)

Dwayne Brown

Headquarters, Washington

202-358-1726

dwayne.c.brown@nasa.gov

DC Agle

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-9011

agle@jpl.nasa.gov

Oct. 7, 2009

RELEASE : 09-232

NASA Refines Asteroid Apophis' Path Toward Earth

PASADENA, Calif. -- Using updated information, NASA scientists have recalculated the path of a large asteroid. The refined path indicates a significantly reduced likelihood of a hazardous encounter with Earth in 2036.

The Apophis asteroid is approximately the size of two-and-a-half football fields. The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA's Jet Propulsion Laboratory in Pasadena, Calif. They will present their updated findings at a meeting of the American Astronomical Society's Division for Planetary Sciences in Puerto Rico on 2009 Oct. 8.

"Apophis has been one of those celestial bodies that has captured the public's interest since it was discovered in 2004," said Chesley. "Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million."

A majority of the data that enabled the updated orbit of Apophis came from observations Dave Tholen and collaborators at the University of Hawaii's Institute for Astronomy in Manoa made. Tholen pored over hundreds of previously unreleased images of the night sky made with the University of Hawaii's 88-inch telescope, located near the summit of Mauna Kea.

Tholen made improved measurements of the asteroid's position in the images, enabling him to provide Chesley and Chodas with new data sets more precise than previous measures for Apophis. Measurements from the Steward Observatory's 90-inch Bok telescope on Kitt Peak in Arizona and the Arecibo Observatory on the island of Puerto Rico also were used in Chesley's calculations.

The information provided a more accurate glimpse of Apophis' orbit well into the latter part of this century. Among the findings is another close encounter by the asteroid with Earth in 2068 with chance of impact currently at approximately three-in-a-million. As with earlier orbital estimates where Earth impacts in 2029 and 2036 could not initially be ruled out due to the need for additional data, it is expected that the 2068 encounter will diminish in probability as more information about Apophis is acquired.

Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029. Additional observations of the asteriod ruled out any possibility of an impact in 2029. However, the asteroid is expected to make a record-setting -- but harmless -- close approach to Earth on Friday, April 13, 2029, when it comes no closer than 18,300 miles above Earth's surface.

"The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL. "The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed."

The science of predicting asteroid orbits is based on a physical model of the solar system which includes the gravitational influence of the sun, moon, other planets and the three largest asteroids.

NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near Earth-Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. Cornell University operates the Arecibo Observatory under a cooperative agreement with the National Science Foundation in Arlington, Va.

For more information about asteroids and near-Earth objects, visit:

http://www.jpl.nasa.gov/asteroidwatch

For more information about NASA, visit:

http://www.nasa.gov

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Russia May Send a Spacecraft to Knock Away Asteroid

AP – FILE - In this Tuesday, Dec. 26, 2006, file photo Russia's Federal Space Agency chief Anatoly Perminov …

By VLADIMIR ISACHENKOV, Associated Press Writer Vladimir Isachenkov, Associated Press Writer – Wed 2009 Dec 30, 9:34 pm ET

MOSCOW – Russia's space agency chief said Wednesday a spacecraft may be dispatched to knock a large asteroid off course and reduce the chances of earth impact, even though U.S. scientists say such a scenario is unlikely.

Anatoly Perminov told Golos Rossii radio the space agency would hold a meeting soon to assess a mission to Apophis. He said his agency might eventually invite NASA, the European Space Agency, the Chinese space agency and others to join the project.

When the 270-meter (885-foot) asteroid was first discovered in 2004, astronomers estimated its chances of smashing into Earth in its first flyby, in 2029, at 1-in-37.

Further studies have ruled out the possibility of an impact in 2029, when the asteroid is expected to come no closer than 18,300 miles (29,450 kilometers) from Earth's surface, but they indicated a small possibility of a hit on subsequent encounters.

NASA had put the chances that Apophis could hit Earth in 2036 as 1-in-45,000. In October, after researchers recalculated the asteroid's path, the agency changed its estimate to 1-in-250,000.

NASA said another close encounter in 2068 will involve a 1-in-330,000 chance of impact.

Don Yeomans, who heads NASA's Near-Earth Object Program, said better calculations of Apophis' path in several years "will almost certainly remove any possibility of an Earth collision" in 2036.

"While Apophis is almost certainly not a problem, I am encouraged that the Russian science community is willing to study the various deflection options that would be available in the event of a future Earth threatening encounter by an asteroid," Yeomans said in an e-mail Wednesday.

Without mentioning NASA's conclusions, Perminov said that he heard from a scientist that Apophis is getting closer and may hit the planet. "I don't remember exactly, but it seems to me it could hit the Earth by 2032," Perminov said.

"People's lives are at stake. We should pay several hundred million dollars and build a system that would allow us to prevent a collision, rather than sit and wait for it to happen and kill hundreds of thousands of people," Perminov said.

Scientists have long theorized about asteroid deflection strategies. Some have proposed sending a probe to circle around a dangerous asteroid to gradually change its trajectory. Others suggested sending a spacecraft to collide with the asteroid and alter its momentum, or hitting it with nuclear weapons.

Perminov wouldn't disclose any details of the project, saying they still need to be worked out. But he said the mission wouldn't require any nuclear explosions.

Hollywood action films "Deep Impact" and "Armageddon," have featured space missions scrambling to avoid catastrophic collisions. In both movies, space crews use nuclear bombs in an attempt to prevent collisions.

"Calculations show that it's possible to create a special purpose spacecraft within the time we have, which would help avoid the collision," Perminov said. "The threat of collision can be averted."

Boris Shustov, the director of the Institute of Astronomy under the Russian Academy of Sciences, hailed Perminov's statement as a signal that officials had come to recognize the danger posed by asteroids.

"Apophis is just a symbolic example, there are many other dangerous objects we know little about," he said, according to RIA Novosti news agency.

___

AP Science Writer Alicia Chang contributed to this story from Los Angeles.

----------------------------------------------------------

BELOW IS JET PROPULSION LABORATORY'S HORIZONS EPHEMERIS GENERATOR

FOR APOPHIS ON 2029 APRIL 13 FROM 5:00 - 6:30PM EDT WHEN APOPHIS IS NOW

CALCULATED TO BE CLOSEST TO THE EARTH. THIS DATA WILL BE UPDATED AND

REVISED AS WE GET CLOSER TO THIS DATE. THE APOPHIS-EARTH DISTANCE IS

LISTED UNDER DELTA AND IS IN ASTRONOMICAL UNITS (AU) WHERE ONE EQUALS

92,955,807 MILES. CLOSEST APPROACH APPEARS TO BE AT 21:45 UT = 5:45 PM EDT.

THE DISTANCE GIVEN OF 0.00025449266589 AU EQUALS ABOUT 23,657 MILES.

Search JPL

HORIZONS Web-Interface

Current Settings

This tool provides a web-based limited interface to JPL's HORIZONS system which can be used to generate ephemerides for solar-system bodies. Full access to HORIZONS features is available via the primary telnet interface. HORIZONS system news shows recent changes and improvements. A web-interface tutorial is available to assist new users.

Object Data Page

JPL/HORIZONS 99942 Apophis (2004 MN4) 2009-Dec-31 00:31:27

Rec #: 99942 (+COV) Soln.date: 2009-Oct-23_11:54:34 # obs: 640 (2004-2008)


FK5/J2000.0 helio. ecliptic osc. elements (AU, DAYS, DEG, period=Julian yrs):


EPOCH= 2453934.5 ! 2006-Jul-18.00 (CT) Residual RMS= .1222

EC= .1910558735070569 QR= .7460589053246545 TP= 2453924.308554644

OM= 204.4601220359806 W= 126.3952531197906 IN= 3.331325896471574

A= .9222625900741523 MA= 11.3411727370707 ADIST= 1.09846627482365

PER= .88571 N= 1.112812986 ANGMOM= .016215639

DAN= 1.00221 DDN= .7981200000000001 L= 330.9016679

B= 2.680995 TP= 2006-Jul-07.8085546


Physical parameters (KM, SEC, rotational period in hours):

GM= n.a. RAD= .135 ROTPER= n.a.

H= 19.7 G= .250 B-V= n.a.

ALBEDO= .330 STYP= n.a.


ASTEROID comments:

1: soln ref.= JPL#144, PHA OCC=0 radar( 2 delay, 5 Dop.)

2: source=ORB

Results

*******************************************************************************

Ephemeris / WWW_USER Thu Dec 31 00:31:28 2009 Pasadena, USA / Horizons

*******************************************************************************

Target body name: 99942 Apophis (2004 MN4) {source: JPL#144}

Center body name: Earth (399) {source: DE405}

Center-site name: GEOCENTRIC

*******************************************************************************

Start time : A.D. 2029-Apr-13 21:00:00.0000 UT

Stop time : A.D. 2029-Apr-13 22:30:00.0000 UT

Step-size : 1 minutes

*******************************************************************************

Target pole/equ : No model available

Target radii : 0.1 km

Center geodetic : 0.00000000,0.00000000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)}

Center cylindric: 0.00000000,0.00000000,0.0000000 {E-lon(deg),Dxy(km),Dz(km)}

Center pole/equ : High-precision EOP model {East-longitude +}

Center radii : 6378.1 x 6378.1 x 6356.8 km {Equator, meridian, pole}

Target primary : Sun {source: DE405}

Interfering body: MOON (Req= 1737.400) km {source: DE405}

Deflecting body : Sun, EARTH {source: DE405}

Deflecting GMs : 1.3271E+11, 3.9860E+05 km^3/s^2

Small perturbers: Ceres, Pallas, Vesta {source: SB405-CPV-2}

Small body GMs : 6.32E+01, 1.43E+01, 1.78E+01 km^3/s^2

Atmos refraction: NO (AIRLESS)

RA format : HMS

Time format : CAL

EOP file : eop.091230.p100323

EOP coverage : DATA-BASED 1962-JAN-20 TO 2009-DEC-30. PREDICTS-> 2010-MAR-22

Units conversion: 1 AU= 149597870.691 km, c= 299792.458 km/s, 1 day= 86400.0 s

Table cut-offs 1: Elevation (-90.0deg=NO ),Airmass (>38.000=NO), Daylight (NO )

Table cut-offs 2: Solar Elongation ( 0.0,180.0=NO )

*******************************************************************************

Initial FK5/J2000.0 heliocentric ecliptic osculating elements (AU, DAYS, DEG):

EPOCH= 2453934.5 ! 2006-Jul-18.00 (CT) Residual RMS= .1222

EC= .1910558735070569 QR= .7460589053246545 TP= 2453924.308554644

OM= 204.4601220359806 W= 126.3952531197906 IN= 3.331325896471574

Asteroid physical parameters (KM, SEC, rotational period in hours):

GM= n.a. RAD= .135 ROTPER= n.a.

H= 19.7 G= .250 B-V= n.a.

ALBEDO= .330 STYP= n.a.

**************************************************************************************************************

Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC APmag S-brt Delta deldot S-O-T /r S-T-O

**************************************************************************************************************

$$SOE

2029-Apr-13 21:00 10 02 01.73 +13 23 59.9 3.78 3.86 0.00028163953313 -2.8432205 124.0732 /T 55.9137

2029-Apr-13 21:01 10 00 13.86 +13 43 58.4 3.79 3.87 0.00028050926716 -2.7923355 123.5450 /T 56.4419

2029-Apr-13 21:02 09 58 24.82 +14 04 03.6 3.79 3.88 0.00027939954534 -2.7407827 123.0123 /T 56.9746

2029-Apr-13 21:03 09 56 34.59 +14 24 15.2 3.80 3.89 0.00027831063552 -2.6885637 122.4750 /T 57.5118

2029-Apr-13 21:04 09 54 43.17 +14 44 33.0 3.81 3.89 0.00027724280395 -2.6356804 121.9334 /T 58.0534

2029-Apr-13 21:05 09 52 50.54 +15 04 56.7 3.82 3.90 0.00027619631710 -2.5821354 121.3873 /T 58.5994

2029-Apr-13 21:06 09 50 56.70 +15 25 26.2 3.82 3.91 0.00027517143993 -2.5279318 120.8369 /T 59.1498

2029-Apr-13 21:07 09 49 01.64 +15 46 01.0 3.83 3.92 0.00027416843528 -2.4730734 120.2822 /T 59.7045

2029-Apr-13 21:08 09 47 05.35 +16 06 41.0 3.84 3.93 0.00027318756544 -2.4175647 119.7232 /T 60.2635

2029-Apr-13 21:09 09 45 07.83 +16 27 25.8 3.85 3.94 0.00027222909013 -2.3614107 119.1599 /T 60.8267

2029-Apr-13 21:10 09 43 09.06 +16 48 15.1 3.86 3.95 0.00027129326738 -2.3046170 118.5925 /T 61.3941

2029-Apr-13 21:11 09 41 09.04 +17 09 08.7 3.87 3.96 0.00027038035189 -2.2471902 118.0211 /T 61.9655

2029-Apr-13 21:12 09 39 07.76 +17 30 06.2 3.87 3.97 0.00026949059678 -2.1891372 117.4455 /T 62.5410

2029-Apr-13 21:13 09 37 05.22 +17 51 07.2 3.88 3.98 0.00026862425151 -2.1304658 116.8660 /T 63.1205

2029-Apr-13 21:14 09 35 01.41 +18 12 11.5 3.90 3.99 0.00026778156277 -2.0711845 116.2826 /T 63.7039

2029-Apr-13 21:15 09 32 56.32 +18 33 18.6 3.91 4.00 0.00026696277276 -2.0113025 115.6953 /T 64.2912

2029-Apr-13 21:16 09 30 49.96 +18 54 28.1 3.92 4.01 0.00026616812105 -1.9508297 115.1043 /T 64.8822

2029-Apr-13 21:17 09 28 42.31 +19 15 39.7 3.93 4.03 0.00026539784229 -1.8897766 114.5096 /T 65.4769

2029-Apr-13 21:18 09 26 33.37 +19 36 53.0 3.94 4.04 0.00026465216707 -1.8281548 113.9112 /T 66.0752

2029-Apr-13 21:19 09 24 23.15 +19 58 07.6 3.95 4.05 0.00026393132138 -1.7659761 113.3094 /T 66.6769

2029-Apr-13 21:20 09 22 11.64 +20 19 23.0 3.97 4.06 0.00026323552548 -1.7032535 112.7042 /T 67.2822

2029-Apr-13 21:21 09 19 58.84 +20 40 38.8 3.98 4.07 0.00026256499524 -1.6400005 112.0956 /T 67.8907

2029-Apr-13 21:22 09 17 44.74 +21 01 54.6 3.99 4.08 0.00026191994056 -1.5762314 111.4838 /T 68.5025

2029-Apr-13 21:23 09 15 29.35 +21 23 09.9 4.01 4.09 0.00026130056550 -1.5119611 110.8689 /T 69.1174

2029-Apr-13 21:24 09 13 12.68 +21 44 24.3 4.02 4.10 0.00026070706797 -1.4472054 110.2509 /T 69.7353

2029-Apr-13 21:25 09 10 54.71 +22 05 37.3 4.03 4.11 0.00026013963964 -1.3819805 109.6300 /T 70.3562

2029-Apr-13 21:26 09 08 35.46 +22 26 48.4 4.05 4.12 0.00025959846477 -1.3163036 109.0064 /T 70.9798

2029-Apr-13 21:27 09 06 14.93 +22 47 57.1 4.07 4.14 0.00025908372157 -1.2501925 108.3800 /T 71.6062

2029-Apr-13 21:28 09 03 53.13 +23 09 03.0 4.08 4.15 0.00025859558045 -1.1836655 107.7511 /T 72.2351

2029-Apr-13 21:29 09 01 30.05 +23 30 05.5 4.10 4.16 0.00025813420443 -1.1167417 107.1197 /T 72.8664

2029-Apr-13 21:30 08 59 05.71 +23 51 04.1 4.12 4.17 0.00025769974876 -1.0494408 106.4860 /T 73.5001

2029-Apr-13 21:31 08 56 40.12 +24 11 58.4 4.13 4.18 0.00025729236076 -0.9817829 105.8501 /T 74.1360

2029-Apr-13 21:32 08 54 13.28 +24 32 47.8 4.15 4.19 0.00025691217935 -0.9137889 105.2121 /T 74.7739

2029-Apr-13 21:33 08 51 45.21 +24 53 31.7 4.17 4.21 0.00025655933517 -0.8454802 104.5722 /T 75.4138

2029-Apr-13 21:34 08 49 15.92 +25 14 09.8 4.19 4.22 0.00025623395006 -0.7768785 103.9304 /T 76.0555

2029-Apr-13 21:35 08 46 45.41 +25 34 41.4 4.21 4.23 0.00025593613706 -0.7080063 103.2870 /T 76.6989

2029-Apr-13 21:36 08 44 13.71 +25 55 06.0 4.23 4.24 0.00025566600014 -0.6388864 102.6421 /T 77.3438

2029-Apr-13 21:37 08 41 40.82 +26 15 23.1 4.25 4.26 0.00025542363402 -0.5695420 101.9958 /T 77.9901

2029-Apr-13 21:38 08 39 06.77 +26 35 32.2 4.27 4.27 0.00025520912407 -0.4999966 101.3482 /T 78.6376

2029-Apr-13 21:39 08 36 31.58 +26 55 32.8 4.29 4.28 0.00025502254607 -0.4302741 100.6996 /T 79.2863

2029-Apr-13 21:40 08 33 55.25 +27 15 24.3 4.31 4.29 0.00025486396627 -0.3603989 100.0499 /T 79.9359

2029-Apr-13 21:41 08 31 17.82 +27 35 06.2 4.33 4.31 0.00025473344098 -0.2903953 99.3995 /T 80.5863

2029-Apr-13 21:42 08 28 39.30 +27 54 38.0 4.36 4.32 0.00025463101672 -0.2202881 98.7484 /T 81.2374

2029-Apr-13 21:43 08 25 59.72 +28 13 59.2 4.38 4.33 0.00025455673011 -0.1501022 98.0968 /T 81.8890

2029-Apr-13 21:44 08 23 19.10 +28 33 09.3 4.40 4.35 0.00025451060767 -0.0798626 97.4448 /T 82.5410

2029-Apr-13 21:45 08 20 37.46 +28 52 07.8 4.43 4.36 0.00025449266589 -0.0095944 96.7926 /T 83.1931

2029-Apr-13 21:46 08 17 54.84 +29 10 54.2 4.45 4.37 0.00025450291121 0.0606772 96.1403 /T 83.8454

2029-Apr-13 21:47 08 15 11.26 +29 29 28.0 4.48 4.39 0.00025454133992 0.1309270 95.4881 /T 84.4976

2029-Apr-13 21:48 08 12 26.76 +29 47 48.8 4.50 4.40 0.00025460793830 0.2011300 94.8361 /T 85.1495

2029-Apr-13 21:49 08 09 41.35 +30 05 56.1 4.53 4.41 0.00025470268236 0.2712611 94.1845 /T 85.8011

2029-Apr-13 21:50 08 06 55.08 +30 23 49.5 4.56 4.43 0.00025482553841 0.3412953 93.5335 /T 86.4521

2029-Apr-13 21:51 08 04 07.98 +30 41 28.5 4.58 4.44 0.00025497646256 0.4112078 92.8831 /T 87.1025

2029-Apr-13 21:52 08 01 20.08 +30 58 52.7 4.61 4.46 0.00025515540106 0.4809743 92.2335 /T 87.7521

2029-Apr-13 21:53 07 58 31.42 +31 16 01.7 4.64 4.47 0.00025536229042 0.5505702 91.5849 /T 88.4007

2029-Apr-13 21:54 07 55 42.04 +31 32 55.1 4.67 4.49 0.00025559705738 0.6199716 90.9374 /T 89.0481

2029-Apr-13 21:55 07 52 51.97 +31 49 32.5 4.70 4.50 0.00025585961918 0.6891549 90.2911 /T 89.6944

2029-Apr-13 21:56 07 50 01.25 +32 05 53.6 4.72 4.52 0.00025614988377 0.7580968 89.6463 /T 90.3392

2029-Apr-13 21:57 07 47 09.93 +32 21 58.1 4.75 4.53 0.00025646774934 0.8267742 89.0030 /T 90.9825

2029-Apr-13 21:58 07 44 18.05 +32 37 45.5 4.78 4.54 0.00025681310530 0.8951648 88.3613 /T 91.6242

2029-Apr-13 21:59 07 41 25.64 +32 53 15.6 4.82 4.56 0.00025718583242 0.9632465 87.7215 /T 92.2640

2029-Apr-13 22:00 07 38 32.75 +33 08 28.2 4.85 4.58 0.00025758580230 1.0309979 87.0835 /T 92.9019

2029-Apr-13 22:01 07 35 39.43 +33 23 22.8 4.88 4.59 0.00025801287826 1.0983979 86.4477 /T 93.5377

2029-Apr-13 22:02 07 32 45.72 +33 37 59.4 4.91 4.61 0.00025846691524 1.1654263 85.8140 /T 94.1714

2029-Apr-13 22:03 07 29 51.67 +33 52 17.6 4.94 4.62 0.00025894776007 1.2320631 85.1827 /T 94.8027

2029-Apr-13 22:04 07 26 57.32 +34 06 17.3 4.98 4.64 0.00025945525182 1.2982892 84.5537 /T 95.4316

2029-Apr-13 22:05 07 24 02.72 +34 19 58.2 5.01 4.65 0.00025998922198 1.3640859 83.9274 /T 96.0580

2029-Apr-13 22:06 07 21 07.91 +34 33 20.1 5.04 4.67 0.00026054949473 1.4294354 83.3037 /T 96.6816

2029-Apr-13 22:07 07 18 12.95 +34 46 23.1 5.08 4.69 0.00026113588711 1.4943204 82.6828 /T 97.3025

2029-Apr-13 22:08 07 15 17.88 +34 59 06.8 5.11 4.70 0.00026174820945 1.5587243 82.0648 /T 97.9205

2029-Apr-13 22:09 07 12 22.75 +35 11 31.1 5.15 4.72 0.00026238626556 1.6226313 81.4498 /T 98.5355

2029-Apr-13 22:10 07 09 27.61 +35 23 36.1 5.18 4.74 0.00026304985299 1.6860261 80.8378 /T 99.1474

2029-Apr-13 22:11 07 06 32.51 +35 35 21.6 5.22 4.75 0.00026373876339 1.7488943 80.2291 /T 99.7561

2029-Apr-13 22:12 07 03 37.50 +35 46 47.6 5.26 4.77 0.00026445278270 1.8112222 79.6237 /T 100.3616

2029-Apr-13 22:13 07 00 42.62 +35 57 54.1 5.29 4.79 0.00026519169157 1.8729967 79.0216 /T 100.9636

2029-Apr-13 22:14 06 57 47.92 +36 08 41.0 5.33 4.80 0.00026595526548 1.9342056 78.4231 /T 101.5621

2029-Apr-13 22:15 06 54 53.45 +36 19 08.3 5.37 4.82 0.00026674327520 1.9948373 77.8280 /T 102.1572

2029-Apr-13 22:16 06 51 59.26 +36 29 16.1 5.41 4.84 0.00026755548700 2.0548811 77.2367 /T 102.7485

2029-Apr-13 22:17 06 49 05.40 +36 39 04.4 5.44 4.86 0.00026839166294 2.1143267 76.6490 /T 103.3362

2029-Apr-13 22:18 06 46 11.91 +36 48 33.3 5.48 4.87 0.00026925156121 2.1731648 76.0651 /T 103.9201

2029-Apr-13 22:19 06 43 18.84 +36 57 42.9 5.52 4.89 0.00027013493633 2.2313868 75.4850 /T 104.5001

2029-Apr-13 22:20 06 40 26.23 +37 06 33.2 5.56 4.91 0.00027104153949 2.2889847 74.9089 /T 105.0762

2029-Apr-13 22:21 06 37 34.13 +37 15 04.4 5.60 4.93 0.00027197111890 2.3459513 74.3368 /T 105.6483

2029-Apr-13 22:22 06 34 42.59 +37 23 16.6 5.64 4.95 0.00027292341995 2.4022799 73.7687 /T 106.2164

2029-Apr-13 22:23 06 31 51.64 +37 31 10.0 5.68 4.96 0.00027389818548 2.4579647 73.2047 /T 106.7804

2029-Apr-13 22:24 06 29 01.33 +37 38 44.7 5.72 4.98 0.00027489515616 2.5130005 72.6448 /T 107.3403

2029-Apr-13 22:25 06 26 11.71 +37 46 00.9 5.76 5.00 0.00027591407071 2.5673826 72.0891 /T 107.8959

2029-Apr-13 22:26 06 23 22.80 +37 52 58.8 5.80 5.02 0.00027695466612 2.6211071 71.5377 /T 108.4473

2029-Apr-13 22:27 06 20 34.65 +37 59 38.5 5.85 5.04 0.00027801667788 2.6741707 70.9906 /T 108.9945

2029-Apr-13 22:28 06 17 47.30 +38 06 00.4 5.89 5.06 0.00027909984030 2.7265707 70.4477 /T 109.5373

2029-Apr-13 22:29 06 15 00.79 +38 12 04.6 5.93 5.08 0.00028020388674 2.7783049 69.9092 /T 110.0758

2029-Apr-13 22:30 06 12 15.14 +38 17 51.3 5.97 5.10 0.00028132854977 2.8293717 69.3751 /T 110.6099

$$EOE

**************************************************************************************************************

Column meaning:


TIME

Prior to 1962, times are UT1. Dates thereafter are UTC. Any 'b' symbol in

the 1st-column denotes a B.C. date. First-column blank (" ") denotes an A.D.

date. Calendar dates prior to 1582-Oct-15 are in the Julian calendar system.

Later calendar dates are in the Gregorian system.

The uniform Coordinate Time scale is used internally. Conversion between

CT and the selected non-uniform UT output scale has not been determined for

UTC times after the next July or January 1st. The last known leap-second

is used over any future interval.

NOTE: "n.a." in output means quantity "not available" at the print-time.


R.A._(ICRF/J2000.0)_DEC =

J2000.0 astrometric right ascension and declination of target center.

Corrected for light-time. Units: HMS (HH MM SS.ff) and DMS (DD MM SS.f)


APmag S-brt =

Asteroid's approximate apparent visual magnitude & surface brightness:

APmag = H + 5*log10(delta) + 5*log10(r) - 2.5*log10((1-G)*phi1 + G*phi2)

In principle, accurate to ~ +/- 0.1 magnitude. For solar phase angles > 90 deg,

the error could exceed 1 magnitude. No values are output for phase angles

greater than 120 degrees, since the errors could be large and unknown.

Units: NONE & VISUAL MAGNITUDES PER SQUARE ARCSECOND


Delta deldot =

Range ("delta") and range-rate ("delta-dot") of target center with respect

to the observer at the instant light seen by the observer at print-time would

have left the target center (print-time minus down-leg light-time); the

distance traveled by a light ray emanating from the center of the target and

recorded by the observer at print-time. "deldot" is a projection of the

velocity vector along this ray, the light-time-corrected line-of-sight from the

coordinate center, and indicates relative motion. A positive "deldot" means the

target center is moving away from the observer (coordinate center). A negative

"deldot" means the target center is moving toward the observer.

Units: AU and KM/S


S-O-T /r =

Sun-Observer-Target angle; target's apparent solar elongation seen from

observer location at print-time. If negative, the target center is behind

the Sun. Angular units: DEGREES.

The '/r' column is a Sun-relative code, output for observing sites

with defined rotation models only.

/T indicates target trails Sun (evening sky)

/L indicates target leads Sun (morning sky)

NOTE: The S-O-T solar elongation angle is the total separation in any

direction. It does not indicate the angle of Sun leading or trailing.


S-T-O =

Sun-Target-Observer (~ PHASE ANGLE) angle: the vertex angle at target center

formed by a vector to the apparent center of the Sun and a vector intersecting

the observer at print-time. This measurable angle is within 20 arcseconds

(0.006 deg) of the reduced PHASE ANGLE at observer's location at print time.

The difference is due to down-leg stellar aberration affecting measured target

position but not apparent solar illumination direction. When computing phase,

Horizons uses the true phase angle, not S-T-O, but the resulting difference

in illuminated fraction is less than 0.001%.

Units: DEGREES

Computations by ...

Solar System Dynamics Group, Horizons On-Line Ephemeris System

4800 Oak Grove Drive, Jet Propulsion Laboratory

Pasadena, CA 91109 USA

Information: http://ssd.jpl.nasa.gov/

Connect : telnet://ssd.jpl.nasa.gov:6775 (via browser)

telnet ssd.jpl.nasa.gov 6775 (via command-line)

Author : Jon.Giorgini@jpl.nasa.gov

**************************************************************************************************************

2009-Dec-31 08:31 UT

(server date/time)

Site Manager:

Webmaster:

Donald K. Yeomans

Alan B. Chamberlin